1. Field of the Invention
Embodiments of the present disclosure generally relate to Volt-Ampere reactive (VAr) compensation and, more particularly, to a method and apparatus for generating on-demand VAr compensation.
2. Description of the Related Art
Current worldwide growth in demand for electricity is leading to a durable increase in energy usage. Due to such increased usage, power levels on the commercial power grid are nearing the maximum capacity of the grid, and building permits to expand on this capacity are becoming more difficult to obtain. The pressure to utilize the existing infrastructure to its maximum is therefore extreme.
Demand Response (DR) is a well-established business model used by utilities to increase the grid efficiency by reducing peak power requirements on the grid. The demand on the grid varies greatly seasonally as well as daily. The ratio between peak consumption, which drives the grid capacity, and least consumption, which usually occurs at night time, can easily reach 2:1. Therefore, it is highly desirable to limit the peak power as much as possible. In the DR model, utilities pay end users to reduce peak load at the utility's request, usually by changing users' thermostat values. A DR operator provides the thermostat and the transmission system required to carry the order. U.S. Pat. No. 4,345,162 discloses an example of DR technology.
Demand response affects the real load that a utility must provide power for, but does not impact a reactive load, which is almost as important. When the loads are not purely resistive, they consume or produce a reactive current which is at +/−90° from the voltage. These reactive currents create many challenges for the utilities, including inducing spurious losses on the lines and the generators, creating stability problems, and affecting the grid voltage. Large users are penalized when they circulate too much reactive current, i.e., the utility imposes a surcharge on the user.
The reactive power generated by a reactive current is the product of the grid voltage multiplied by the reactive current and is measured in Volt-Ampere reactive (VAr). Utilities do not charge for reactive power but can suffer greatly from its consequences. In order to offset the VArs created by the reactive loads, utilities deploy a large number of VAr compensators. They also use these VAr compensators to stabilize the grid and control the voltage. In addition, there is also a market to trade reactive power between utilities. VAr compensators are typically used at substations and at the large customer facilities. VAr compensators may comprise banks of capacitors, or Static Synchronous Compensators (STATCOMs), or static VAr compensators (SVCs).
With the advent of distributed renewable power generation, users may generate power and couple such generated power to the commercial power grid to sell power to the commercial power company. However, existing standards for distributed generators (DGs) usually prohibit the DG from generating reactive currents, leaving the utility to only see the reactive part of the load if the DG is offsetting the real load.
Therefore, there is a need in the art for a method and apparatus for utilizing DGs for generating on-demand VAr compensation.